An appropriate summary for the article "A Most Troublesome Element" is the last option - C. Arsenic is a naturally occurring, poisonous element that has threatened the health of humans since the Middle Ages.
It clearly states what the whole article is about.
The answer is C. The first one is totally a fragment!
Mirroring is a communication technique that is often attributed to the field of Neuro-Linguistic Programming. <span>The purpose of mirroring is in, essence, to improve rapport with another person by imitating the other person's physical positions and mannerisms, and/or imitating the other person's verbal approach and style.</span>
